Deep gravitational processes in the Maratea Valley (Southern Italy): evidence from high resolution reflection seismic profiling of the surrounding offshore

Deep gravitational deformations (DGPV; sackung, gravitational spreadings, gleistung) are interpreted in terms of superficial landslides and gravitational tectonics.These movements have been singled out in many outcrops of Italy, mainly referring to their distribution on the territory and to geomorphological aspects (Dramis et al., 1983), in central and southern Apennines (Forcella et al., 1982; Agnesi et al., 1987; Calamita et al., 1982; Guerricchio and Melidoro, 1979). Among their main characteristics there are the great volume of the involved masses, the very ancient age of the deformations, the slow evolution during geologic time (of a deep-seated creep type), the persistence of gravity instability conditions through time and the movement reactivations during seismic and meteoric events. The Maratea Valley (Basilicata) is characterized by deep gravitational movements involving the Meso-Cenozoic calcareous-dolomitic formations (tectonic units "Alburno-Cervati" and "Bulgheria-Verbicaro") interpreted as sackung-type phenomena. The complex morpho-structural setting of the area has been influenced by the Pleistocene extensional tectonics, probably still active. The tectonic dislocations, characterized by a strike-slip component at a regional scale, have caused the superimposition of the Bulgheria-Verbicaro unit on the Crete Nere Formation and the tectonic contact of the last formation on the Alburno-Cervati Unit, cropping out on the right flank of the valley. Normal faulting, block rotations and structural widening are produced as an effect of differential velocity during strike-slip tectonics. The Crete Nere flysch (Liguride Units) takes on plastic behaviour due to high water contents. It is affected by a flow-type, relatively deep process (30-50 m) within the valley and near the sea. High resolution multichannel seismic profiles, coupled to Subbottom Chirp sections have provided new insights on offshore prolongation of the Maratea Valley and related landslides. Late Pleistocene-Holocene slope sequences deposited in an intra-slope basin and then appear to be tectonically uplifted in correspondence to complex morpho-structural highd controlled by normal faults. Three main seismo-stratigraphic units, representing the sedimentary cover overlie a rocky acoustic basement, characterized by two main acoustic facies and truncated by a wide erosional surface, referred to the isotopic substage 5e have been recognized (Aiello et al., 2010).